These studies are designed to understand the mechanisms of H ion buffering in the brain and CSF in respiratory acidosis and alkalosis. Since the primary central drive to ventilation is related to (H ion) in the medulla, factors influencing (H ion) in the CNS become important in the central chemical control of breathing. The studies are conducted in pentobarbital-anesthetized dogs in states of respiratory acidosis (10% CO2 at constant VA) or respiratory alkalosis (mechanical hyperventilation to PaCO2 approximately 20). In respiratory acidosis the role of ammonia as a buffer in the CNS and as a primary respiratory stimulant is under investigation. The HCO3 negative ion concentration in the CSF and its relationship to simultaneous changes in blood HCO3 negative ion in respiratory acid-base disturbance is being investigated by selectively increasing, lowering or keeping constant the plasma HCO3 negative ion level. The role of carbonic anhydrase in the choroid plexus and glial cells of the brain in formation of HCO3 negative ion in the CNS is also being investigated in instances of respiratory acidosis. This is done by inhibiting carbonic anhydrase by infusion of acetazolamide into the cerebral ventricles.